1. Field of the Invention
The present invention relates to thin-film magnetic heads, and more particularly, the invention relates to an inductive head which applies a recording magnetic field to a magnetic recording medium.
2. Description of the Related Art
As shown in FIG. 27, a conventional thin-film inductive head includes a lower core layer 82, an upper core layer 83, and a coil layer 88 provided between the lower core layer 82 and the upper core layer 83. The lower core layer 82 has a uniform thickness.
A nonmagnetic gap depth-defining layer (hereinafter referred to as Gd-defining layer) 87 is formed on the lower core layer 82 at a position away from the front end of the lower core layer 82. A lower magnetic pole layer 84 and a gap layer 85 are deposited in that order on the lower core layer 82 in front of the Gd-defining layer 87.
An upper magnetic pole layer 86 includes a front region (pole region) 86a which has a width corresponding to the track width Tw and which is formed on and in contact with the gap layer 85, and a magnetic gap G is formed between the front region 86a of the upper magnetic pole layer 86 and the lower magnetic pole layer 84.
The upper magnetic pole layer 86 also includes a back region 86b which has a width that is larger than the track width Tw and which is formed on and in contact with the Gd-defining layer 87. An upper core layer 83 is connected to the upper surface of the upper magnetic pole layer 86.
In such a thin-film magnetic head, when magnetic information is written into a recording medium, a recording current is applied to the coil layer 88, and a recording magnetic field is induced to the upper corer layer 83 and the lower core layer 82 by the recording current. The recording magnetic field flows from the upper core layer 83 into the upper magnetic pole layer 86, and a leakage magnetic field from the upper magnetic pole layer 86 is applied to the recording medium from the magnetic gap G.
In the conventional thin-film magnetic head, in order to cope with higher recording densities, the upper magnetic pole layer 86 is desirably composed of a magnetic material having high saturation magnetization. However, in the thin-film magnetic head having the conventional structure shown in FIG. 27, if the upper magnetic pole layer 86 is formed so as to have high saturation magnetization, the leakage magnetic field from the upper magnetic pole layer 86 is applied to the recording medium from sections other than the magnetic gap G. This condition is known as “side fringing” in which the width of the recording magnetic field applied to the recording medium exceeds the track width Tw.